Preheat oven to 350° and butter a 9x13-inch baking dish.,Combine Champagne, butter, bay leaf, parsley, onion and celery in a saucepan; bring to a boil, reduce heat and simmer until reduced by half; remove the bay leaf and add the cream, remove pan from the stove.,Rinse then dry fish with paper towels and sprinkle with salt and pepper; arrange in one layer in the baking dish.,Add the mushrooms to the sauce and pour the sauce over the fillets; sprinkle with cheese.,______